Merge "Wait until the thread is waiting before issuing next task" into main

2 files changed, 34 insertions, 5 deletions

diff --git a/services/core/java/com/android/server/wm/PersisterQueue.java b/services/core/java/com/android/server/wm/PersisterQueue.java
index 9dc3d6a81338..bc16a566bfef 100644
--- a/services/core/java/com/android/server/wm/PersisterQueue.java
+++ b/services/core/java/com/android/server/wm/PersisterQueue.java
@@ -86,6 +86,34 @@ class PersisterQueue {
         mLazyTaskWriterThread = new LazyTaskWriterThread("LazyTaskWriterThread");
     }
 
+    /**
+     * Busy wait until {@link #mLazyTaskWriterThread} is in {@link Thread.State#WAITING}, or
+     * times out. This indicates the thread is waiting for new tasks to appear. If the wait
+     * succeeds, this queue waits at least {@link #mPreTaskDelayMs} milliseconds before running the
+     * next task.
+     *
+     * <p>This is for testing purposes only.
+     *
+     * @param timeoutMillis the maximum time of waiting in milliseconds
+     * @return {@code true} if the thread is in {@link Thread.State#WAITING} at return
+     */
+    @VisibleForTesting
+    boolean waitUntilWritingThreadIsWaiting(long timeoutMillis) {
+        final long timeoutTime = SystemClock.uptimeMillis() + timeoutMillis;
+        do {
+            Thread.State state;
+            synchronized (this) {
+                state = mLazyTaskWriterThread.getState();
+            }
+            if (state == Thread.State.WAITING) {
+                return true;
+            }
+            Thread.yield();
+        } while (SystemClock.uptimeMillis() < timeoutTime);
+
+        return false;
+    }
+
     synchronized void startPersisting() {
         if (!mLazyTaskWriterThread.isAlive()) {
             mLazyTaskWriterThread.start();
diff --git a/services/tests/wmtests/src/com/android/server/wm/PersisterQueueTests.java b/services/tests/wmtests/src/com/android/server/wm/PersisterQueueTests.java
index 3e87f1f96fcd..ee9673f5ee77 100644
--- a/services/tests/wmtests/src/com/android/server/wm/PersisterQueueTests.java
+++ b/services/tests/wmtests/src/com/android/server/wm/PersisterQueueTests.java
@@ -177,15 +177,16 @@ public class PersisterQueueTests {
         assertTrue("Target didn't call callback enough times.",
                 mListener.waitForAllExpectedCallbackDone(TIMEOUT_ALLOWANCE));
 
+        // Wait until writing thread is waiting, which indicates the thread is waiting for new tasks
+        // to appear.
+        assertTrue("Failed to wait until the writing thread is waiting.",
+                mTarget.waitUntilWritingThreadIsWaiting(TIMEOUT_ALLOWANCE));
+
         // Second item
         mFactory.setExpectedProcessedItemNumber(1);
         mListener.setExpectedOnPreProcessItemCallbackTimes(1);
         dispatchTime = SystemClock.uptimeMillis();
-        // Synchronize on the instance to make sure we schedule the item after it starts to wait for
-        // task indefinitely.
-        synchronized (mTarget) {
-            mTarget.addItem(mFactory.createItem(), false);
-        }
+        mTarget.addItem(mFactory.createItem(), false);
         assertTrue("Target didn't process item enough times.",
                 mFactory.waitForAllExpectedItemsProcessed(PRE_TASK_DELAY_MS + TIMEOUT_ALLOWANCE));
         assertEquals("Target didn't process all items.", 2, mFactory.getTotalProcessedItemCount());